1. Field of the Invention
The present invention relates to a new styryl polymer having charge-transporting ability and/or photoconductive ability, a production method thereof. Further the present invention provides an organic electrolumnescense element and photosensitive member in application of the styryl polymer compound.
2. Description of the Prior Art
Organic materials having charge-transporting ability or photoconductive ability have many advantages such as low cost, possibility of many processings and no pollution. Many such compounds are proposed, such as oxadiazole, hydrazones, pyrazolines, oxazoles, arylamines, benzidines, stilbenes, butadienes.
There are proposed a photosensitive member and organic photosensitive member using the above characteristics of organic compounds.
The electrophotographic system is one of image forming methods invented by Carlson. This system comprises electrically charging a photosensitive member by means of corona discharge, irradiating the photosensitive member according to the images to form electrostatic latent images, adhering toner particles to the electrostatic latent images for developing and transferring toner particles to paper.
Basic characteristics required for such a photosensitive member in electrophotography is as follows; an adequate potential is kept in the dark, few electrocharges are scattered and electrocharges can be dissipated rapidly by photoirradiation.
Conventional photosensitive members use inorganic photoconductive materials such as selenium, selenium alloy, cadmium sulfide or zinc oxide. These photoconductive materials have many advantages such as durability with respect to copy. However, they have disadvantages such as high production costs are low processability and poison.
In order to overcome the above disadvantages, organic photoconductor are developed. A photosensitive member using the conventional organic photoconductive materials as a charge transporting material are, however, not satisfactory in electrophotographic characteristics such as chargeability, sensitivity and residual potential. It is desired that charge transporting materials excellent in charge-transporting ability and durability are developed.
As a technique using charge-transporting ability of organic materials, organic electroluminescence element is known. Such a organic electroluminescence element is studied enthusiastic because it may be a full-color solid-type large display of low cost.
In general, the organic electroluminescence element is composed of a luninous layer and a pair of electrodes sandwiching the luninous layer. When voltage is applied to the electrodes, electrons are injected from cathode and holes are injected from anode. The electrons and hole are recombined in the luninous layer. Energy level is return from conductive band to valence band to emit light as luminescence.
Conventional organic electroluminescence elements has high driving voltage, poor luminous brightness And low luninous efficiency, compared with inorganic electroluminescence elements. Deterioration of characteristics are remarkable, resulting in failure to put it into practical use.
Recently attention is paid to organic electroluminescence element with thin layers laminated, which contains organic materials showing high fluorescent quantum yield at low voltage of 10 V or less to emit light, being reported by Applied Physics Letters, Vol. 51, page 913, 1998.
In the report, a metal chelate compound is contained in fluorescent layer and amine compound is contained in a hole-injecting layer, resulting in achievement of green color light emmision of high brightness, and showing several hundreds of brightness (cd/m.sup.2) and maximum luminous efficiency of 1.51 m/W. This performance is nearly practical.
Conventional organic electroluminescence element has been improved in luminous strength through improvement of construction. However, satisfactory brightness has not been achieved yet. There is also a big problem on stability when repeatedly used.
Therefore, a charge transporting material with excellent charge transporting ability and durability is desired to be developed in order to develop organic electroluminescence elements having higher luminous brightness and stability when repeatedly used.